LXR linux/arch/mips/kernel/time.c

   1// SPDX-License-Identifier: GPL-2.0-or-later
   2/*
   3 * Copyright 2001 MontaVista Software Inc.
   4 * Author: Jun Sun, jsun@mvista.com or jsun@junsun.net
   5 * Copyright (c) 2003, 2004  Maciej W. Rozycki
   6 *
   7 * Common time service routines for MIPS machines.
   8 */
   9#include <linux/bug.h>
  10#include <linux/clockchips.h>
  11#include <linux/types.h>
  12#include <linux/kernel.h>
  13#include <linux/init.h>
  14#include <linux/sched.h>
  15#include <linux/param.h>
  16#include <linux/time.h>
  17#include <linux/timex.h>
  18#include <linux/smp.h>
  19#include <linux/spinlock.h>
  20#include <linux/export.h>
  21#include <linux/cpufreq.h>
  22#include <linux/delay.h>
  23
  24#include <asm/cpu-features.h>
  25#include <asm/cpu-type.h>
  26#include <asm/div64.h>
  27#include <asm/time.h>
  28
  29#ifdef CONFIG_CPU_FREQ
  30
  31static DEFINE_PER_CPU(unsigned long, pcp_lpj_ref);
  32static DEFINE_PER_CPU(unsigned long, pcp_lpj_ref_freq);
  33static unsigned long glb_lpj_ref;
  34static unsigned long glb_lpj_ref_freq;
  35
  36static int cpufreq_callback(struct notifier_block *nb,
  37                            unsigned long val, void *data)
  38{
  39        struct cpufreq_freqs *freq = data;
  40        struct cpumask *cpus = freq->policy->cpus;
  41        unsigned long lpj;
  42        int cpu;
  43
  44        /*
  45         * Skip lpj numbers adjustment if the CPU-freq transition is safe for
  46         * the loops delay. (Is this possible?)
  47         */
  48        if (freq->flags & CPUFREQ_CONST_LOOPS)
  49                return NOTIFY_OK;
  50
  51        /* Save the initial values of the lpjes for future scaling. */
  52        if (!glb_lpj_ref) {
  53                glb_lpj_ref = boot_cpu_data.udelay_val;
  54                glb_lpj_ref_freq = freq->old;
  55
  56                for_each_online_cpu(cpu) {
  57                        per_cpu(pcp_lpj_ref, cpu) =
  58                                cpu_data[cpu].udelay_val;
  59                        per_cpu(pcp_lpj_ref_freq, cpu) = freq->old;
  60                }
  61        }
  62
  63        /*
  64         * Adjust global lpj variable and per-CPU udelay_val number in
  65         * accordance with the new CPU frequency.
  66         */
  67        if ((val == CPUFREQ_PRECHANGE  && freq->old < freq->new) ||
  68            (val == CPUFREQ_POSTCHANGE && freq->old > freq->new)) {
  69                loops_per_jiffy = cpufreq_scale(glb_lpj_ref,
  70                                                glb_lpj_ref_freq,
  71                                                freq->new);
  72
  73                for_each_cpu(cpu, cpus) {
  74                        lpj = cpufreq_scale(per_cpu(pcp_lpj_ref, cpu),
  75                                            per_cpu(pcp_lpj_ref_freq, cpu),
  76                                            freq->new);
  77                        cpu_data[cpu].udelay_val = (unsigned int)lpj;
  78                }
  79        }
  80
  81        return NOTIFY_OK;
  82}
  83
  84static struct notifier_block cpufreq_notifier = {
  85        .notifier_call  = cpufreq_callback,
  86};
  87
  88static int __init register_cpufreq_notifier(void)
  89{
  90        return cpufreq_register_notifier(&cpufreq_notifier,
  91                                         CPUFREQ_TRANSITION_NOTIFIER);
  92}
  93core_initcall(register_cpufreq_notifier);
  94
  95#endif /* CONFIG_CPU_FREQ */
  96
  97/*
  98 * forward reference
  99 */
 100DEFINE_SPINLOCK(rtc_lock);
 101EXPORT_SYMBOL(rtc_lock);
 102
 103static int null_perf_irq(void)
 104{
 105        return 0;
 106}
 107
 108int (*perf_irq)(void) = null_perf_irq;
 109
 110EXPORT_SYMBOL(perf_irq);
 111
 112/*
 113 * time_init() - it does the following things.
 114 *
 115 * 1) plat_time_init() -
 116 *      a) (optional) set up RTC routines,
 117 *      b) (optional) calibrate and set the mips_hpt_frequency
 118 *          (only needed if you intended to use cpu counter as timer interrupt
 119 *           source)
 120 * 2) calculate a couple of cached variables for later usage
 121 */
 122
 123unsigned int mips_hpt_frequency;
 124EXPORT_SYMBOL_GPL(mips_hpt_frequency);
 125
 126static __init int cpu_has_mfc0_count_bug(void)
 127{
 128        switch (current_cpu_type()) {
 129        case CPU_R4000PC:
 130        case CPU_R4000SC:
 131        case CPU_R4000MC:
 132                /*
 133                 * V3.0 is documented as suffering from the mfc0 from count bug.
 134                 * Afaik this is the last version of the R4000.  Later versions
 135                 * were marketed as R4400.
 136                 */
 137                return 1;
 138
 139        case CPU_R4400PC:
 140        case CPU_R4400SC:
 141        case CPU_R4400MC:
 142                /*
 143                 * The published errata for the R4400 up to 3.0 say the CPU
 144                 * has the mfc0 from count bug.
 145                 */
 146                if ((current_cpu_data.processor_id & 0xff) <= 0x30)
 147                        return 1;
 148
 149                /*
 150                 * we assume newer revisions are ok
 151                 */
 152                return 0;
 153        }
 154
 155        return 0;
 156}
 157
 158void __init time_init(void)
 159{
 160        plat_time_init();
 161
 162        /*
 163         * The use of the R4k timer as a clock event takes precedence;
 164         * if reading the Count register might interfere with the timer
 165         * interrupt, then we don't use the timer as a clock source.
 166         * We may still use the timer as a clock source though if the
 167         * timer interrupt isn't reliable; the interference doesn't
 168         * matter then, because we don't use the interrupt.
 169         */
 170        if (mips_clockevent_init() != 0 || !cpu_has_mfc0_count_bug())
 171                init_mips_clocksource();
 172}
 173